ANNUAL REPORT, 1947-48 53 



of a tin compound were compared with similar untreated glass containers to 

 determine the effects of the tin treatment on ascorbic acid, color, and flavor 

 retentions of various foodstuffs packed in these containers. No signifacani 

 differences were observed in apple juice, orange juice, asparagus, grapefruit 

 juice, strawberries, green beans, and tomato juice, which were the foods selected 

 for the study. The maximum amount of tin recovered from any of the foods 

 packed in the treated containers was 5 p. p.m. from green beans which had been 

 stored at 100°F. for six months. 



Spectral studies on amber glass bottles indicated that the tin treatment did 

 not appreciably affect the light transmission characteristics of these containers. 



The Effect of Processing Conditions of Time and Temperature Upon The 

 Enzyme Systems of Canned Acid Foods. (W. B. Esselen, Jr., A. M. Kaplan, 

 and J. E. W. McConnell.) Processing times and temperatures for acid fruits, 

 vegetables, and juices have usually been developed with the purpose of destroy- 

 ing or inhibiting the growth of microorganisms present in the food. With the 

 exception of a few isolated foods and enzymes, little thought has been given to 

 the effect of the process upon the enzyme systems involved, the assumption being 

 that the enzyme systems are destroyed during the processing. Since it is known 

 that enzymes play an important role in the deterioration of acid foods, the effect 

 of heat processing on the principal enzyme systems of a representative group of 

 acid foods was investigated. The investigation was further motivated by the 

 possibility that the data obtained could be applied to the development of one of 

 the enz3'me systems as an indicator of adequate processing of canned acid foods. 



As a result of this investigation a method has been developed for the deter- 

 mination of the thermal destruction conditions of the ascorbic acid oxidase and 

 peroxidase of some acid foods that should find application in thermal destruction 

 studies o£ the enzyme systems of other foods and biological systems. Thermal 

 destruction curves of the enzyme systems studied follow a straight line within 

 certain temperature limits when plotted on semi-logarithimc paper and are af- 

 fected by some substances that are added to foods during canning. The pro- 

 cessing requirements of time and temperature necessary to inactivate the peroxi- 

 dase of experimental packs of acid foods processed under practical conditions 

 can be accurately determined through the use of standard methods of process 

 time determinations. 



Influence of Food Ingredients on the Heat Resistance of Spoilage Organisms 

 Encountered in Canned Acid Foods. (E. E. Anderson and W. B. Esselen, Jr.) 

 Thermal death rate characteristics of suspensions of selected yeasts and bacteria 

 were observed as they were affected by changes of the pH of the media from 3.0 

 to 7.0 and by various concentrations of salt (1 to 8 percent). At 140°F. the end- 

 point of destruction (99.99 percent) of a suspension of Saccharoniyces cerevisiae 

 occurred within seven minutes in Mcllvaine's buffer at pH 3.0. At pH 7.0, 40 

 percent longer time was required to accomplish the same degree of destruction. 



Salt (NaCI) added to tomato juice in concentrations ranging from 1 to 8 

 percent caused a definite drop in pH, amounting to 0.4 to 0.5 pH units in the case 

 of 8 percent added salt. An increased rate of destruction at all test temperatures 

 (200° to 220°F.) was noted for suspensions of Bacillus thermoacidurans in tomato 

 juice with added salt, particularly that containing 8 percent salt, in which case 

 99.99 percent destruction at 212°F. was effected in 60 percent of the time required 

 by control suspensions in plain tomato juice. 



Sterilizing Value of Come-Up Time in Processing Home-Canned Foods. 



(J. E. W. McConnell, N. A. Vanasse, and W. B. Esselen, Jr.) Preliminary in- 



